The pi-Cell: A Fast Liquid-Crystal Optical-Switching Device

Bos, Philip J.; Koehler/beran, K. Rickey

doi:10.1080/00268948408071693

Cited by 306 publications

(119 citation statements)

References 7 publications

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“…So far, a Frederiks tran sition was studied. In view of the interest for display applications, the study of the 7r-cell and analogous devices [21] as well as of supertwisted cells is desirable. Furthermore, the director field under the influence of a strong laser field as observed in nonlinear optical experiments [22] can be treated.…”

Section: Discussionmentioning

confidence: 99%

Derivation and Application of an Algorithm for the Numerical Calculation of the Local Orientation of Nematic Liquid Crystals

Kilian

Hess

1989

Zeitschrift Für Naturforschung A

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D e r iv a tio n a n d A p p lic a tio n o f a n A lg o rith m fo r th e N u m e ric a l C a lc u la tio n o f th e L o c a l O r ie n ta tio n o f N e m a tic L iq u id C r y s ta ls A. Kilian and S. Hess Institut für Theoretische Physik, Technische Universität Berlin, Berlin Z. Naturforsch. 44 a, 693 -703 (1989); received June 16, 1989 Starting from a relaxation equation for the alignment tensor, an algorithm is derived which allows the numerical calculation of the dynamic and static behavior of the director field n with the correct nematic symmetry property, where n and -n are equivalent. As a first application, a two-dimensio nal problem is treated where the typical nematic defects with half-integer winding numbers only occur when the algorithm with the correct nematic symmetry property is used. Furthermore, the method is applied to the static and dynamic behavior of a Frederiks cell with strong and weak anchoring.

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Section: Discussionmentioning

confidence: 99%

Derivation and Application of an Algorithm for the Numerical Calculation of the Local Orientation of Nematic Liquid Crystals

Kilian

Hess

1989

Zeitschrift Für Naturforschung A

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“…In OCB, the pre-tilt angle must be larger (.8 6 ), and it only operates between the bend deformation and homeotropic state. 57 Due to the alignment configuration of OCB, the backflow effect is eliminated such that faster responses can be achieved. In the OCB configuration, the flow accelerates the relaxation motion of molecules due to a torque-like force in the mid-layer.…”

Section: Ocbmentioning

confidence: 99%

“…The pi-cell was first proposed 57 in 1984. The LC is aligned to produce a bend structure in the middle of this typical cell.…”

Section: Ocbmentioning

confidence: 99%

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

2014

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This paper describes the fundamentals of phase-only liquid crystal on silicon (LCOS) technology, which have not been previously discussed in detail. This technology is widely utilized in high efficiency applications for real-time holography and diffractive optics. The paper begins with a brief introduction on the developmental trajectory of phase-only LCOS technology, followed by the correct selection of liquid crystal (LC) materials and corresponding electro-optic effects in such devices. Attention is focused on the essential requirements of the physical aspects of the LC layer as well as the indispensable parameters for the response time of the device. Furthermore, the basic functionalities embedded in the complementary metal oxide semiconductor (CMOS) silicon backplane for phase-only LCOS devices are illustrated, including two typical addressing schemes. Finally, the application of phase-only LCOS devices in real-time holography will be introduced in association with the use of cutting-edge computer-generated holograms. The architecture of LCOS devices is similar to conventional LC devices except that a silicon backplane constitutes one of the substrates (Figure 1). The silicon CMOS backplane consists of the electronic circuitry that is buried underneath pixel arrays to provide a high 'fill factor'. The pixels are aluminum mirrors deposited on the surface of the silicon backplane. The incident light is transmitted through the LC layer with almost zero absorption. The integration of high-performance driving circuitry allows the applied voltage to be changed on each pixel, thereby controlling the phase retardation of the incident wavefront across the device. Currently, there are two types of light modulation using LCOS devices, amplitude modulation and phase modulation. In the former case, the amplitude of the light signal is modulated 6,7 by varying the linear polarzation direction of the incident light passing through a linear polarizer, the same principle used in a standard LC television. In the latter case, the phase delay is accomplished by electrically adjusting the optical refractive index along the light path, which is possible because of the non-zero birefringence of the LC materials in use but should be carefully characterized. [8][9][10][11][12][13] In a phase-only LCOS SLM modulator, no light absorption by polarizers or other light-absorbing components will occur, such that the maximum light efficiency can be expected.Currently, most of the conventional LC devices are not able to efficiently modulate the phase of an incident wavefront. For instance, the LC device structure using thin film transistors is not suitable for phase modulation because an appropriate electro-optic effect has not been used (see the section on 'Twisted nematic (TN) configuration' and the section on 'VAN configuration' for details). Moreover, the pixels of this type of device are too large to provide acceptably large diffraction angles. In addition, the pixel circuitry and connection tracks are in the light path such that the ...

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“…(3) [14][15][16] and hence |(e 1 + e 3 )| can thus be found. Some of the commonly used techniques for finding |(e 1 − e 3 )| include measurements of the in-plane tilt of the optic axis of a chiral nematic LC when the molecules are aligned in a uniform lying helical (ULH) configuration [17] or in a Twisted Nematic (TN)/Hybrid Aligned Nematic (HAN) cell, while the sum |(e 1 + e 3 )| can be determined using HAN or π cells [18]. The ULH configuration is easily realizable in achiral bent-core systems by doping with a commercially available chiral dopant with a significantly larger twisting power.…”

Section: Flexoelectricitymentioning

confidence: 99%

Effect of cybotactic clusters on the elastic and flexoelectric properties of bent-core liquid crystals belonging to the same homologous series

et al. 2013

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We report results of the splay (K 11 ) and bend (K 33 ) elastic constants and the effective flexoelectric coefficient of three bent-core liquid crystals belonging to a homologous series of 4-cyanoresorcinol bisbenzoates with varying chain lengths. Based on the results of x-ray scattering studies, one of the three compounds with a shorter chain length (C4) has few, if any, clusters present in its nematic phase and behaves quite normally, whereas the others two with longer chain lengths (C6 and C7) show the presence of cybotactic nematic phase with smectic C type clusters. These grow in size with a reduction in temperature. K 33 is found to be the least for C7, whereas it is weakly dependent on temperature. K 33 is somewhat higher for C4 and C6 and is almost independent of temperature. K 11 for C6 and C7 is higher by 20% to 50% than C4 depending on the temperature. K 11 increases linearly with a reduction in temperature for the three compounds. For C6 K 11 > K 33 by a factor up to ∼2 depending on the temperature, for C4 it is greater by a factor up to 1.3, and for C7 it is greater by a factor of ∼2.5. These results suggest that the clusters do not have any effect on K 11 . The magnitude of the effective flexoelectric coefficient e = (|e 1 − e 3 |) is measured by creating a uniform lying helix (ULH) configuration in a planar cell. By doping the bent-core system with a small wt% of a chiral dopant, the ULH is obtained by cooling planar cells to the cholesteric phase under weak electric field. The effective flexoelectric coefficient is greater for the bent-core systems than for calamatics but it is much lower than would otherwise have been expected for such systems. |e 1 − e 3 | for C4 > C6 ≈ C7 is greater by 20% to 25% than C6 and C7 at the same reduced temperature. These differences in the effective flexoelectric coefficient can easily arise from a difference in the chain lengths among the members of the series but if the presence of clusters were to have an influence on |e 1 − e 3 |, then these would reduce it, contrary to the expectations for the bent-core systems.

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The pi-Cell: A Fast Liquid-Crystal Optical-Switching Device

Cited by 306 publications

References 7 publications

Derivation and Application of an Algorithm for the Numerical Calculation of the Local Orientation of Nematic Liquid Crystals

Derivation and Application of an Algorithm for the Numerical Calculation of the Local Orientation of Nematic Liquid Crystals

Fundamentals of phase-only liquid crystal on silicon (LCOS) devices

Effect of cybotactic clusters on the elastic and flexoelectric properties of bent-core liquid crystals belonging to the same homologous series

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